The Effect Of GA₄₊₇ And NAA Treatment On The Development And Sugar Metabolism Of Peach Fruit

Peach(Prunus persica)is one of the drupe fruit plants classified in rosaceae family.It is one of the most important fruits in the world.Peach fruit quality including several aspects such as flavor,texture and aroma which influence the development of peach industry.The concentration and composition of soluble sugar are important parts of the fruit flavor,and sugar accumulation is the key to peach fruit quality formation.Sugar accumulation process can be affected by complex external factors.External stimulationof fruit sugar metabolism related enzymes,the effects of the sugar content in fruit,key genes and regulation process in sugar accumulation is detected.Many similar researches have been performed in many fruit trees,but there are few related researches in sugar accumulation of peach fruit.Therefore,the experimental study is meaningful.Two Prunus persica(L.)Batsch cultivars with different ripening time and sugar content performance were selected for this study:the early maturity cultivar'Huyou 018'and the late maturity cultivar 'Jinxiu' yellow peach.Both of two cultivars are the main commercial cultivars in China.Different concertration solutions of GA4+7(0.5 mM/L?0.75 mM/L?1.25 mM/L)and NAA(0.25 mM/L?0.5 mM/L?1 mM/L?2 mM/L)were sprayed onto young fruit 30 days after full blossom.Contents of different sugar composition and expression levels of sugar related genes were evaluated,as well as correlation analysis was conducted of these two values.The effect of exogenous hormones treatments on the sugar metabolism of peach were evaluated both at the physiological and melocular levels.Molecule level,physiology index,concentration of soluble sugar,and expression of sugar metabolism related gene were observed and recorded after exogenous hormone treatment.The main results were as follows.1.NAA treatments of 1 mM/L and 2 mM/L leaded the peach fruit to withering and fall off,which indicated that they are not suitable for young peach fruit.2.Both hormone treatments did not affect soluble sugar composition of peach fruit.3.For 'Jinxiu'yellow peach,1.25 mM/L GA4+7treatmentsignificantly increased the fruit weight,fruit firmness,TSS,longitudinal diameter,transverse diameter and lateral diameter.While 0.5 mM/L NAA treatment reduced the fruit weight,TSS,fruit diameter.For 'Huyou 018',all three different concentrations of GA4+7 treatment reduced the fruit transverse diameter,while GA4+7 treatment significantly reduced the fruit firmness.0.25 mM/L NAA treatment significantly increased the fruit weight,fruit longitudinal diameter and transverse diameter.0.5 mM/L NAA treatment significantly reduced fruit weight.TSS treatment significantly reduce the longitudinal diameter and transverse diameter.4.For 'Jinxiu' yellow peach,1.25 mM/L GA4+7 treatment significantly increased the content of sucrose andreduced the glucose content.The fructose content in the middle period of fruit development was also lower than control.The sorbitol concentration increased on the later and maturity period of fruit development.Under 0.5 mM/L NAA treatment,the sucrose concentration reduced,while the sorbitol concentration increased in the late period of fruit development.The inhibited impact of glucose accumulation increased with the increase of NAA concertration.5.For 'Huyou 018',1.25 mM/L GA4+7 treatment significantly increased the sucrose concentration in the whole development and growth stages and glucose level at the late development stage.0.5 mM/L GA4+7 significantly increased fructose concentration before fruit expansion stage.GA4+7 treatment mainly inhibit sorbitol content on fruit development of late mature period.0.25 mM/L NAA treatment significantly promote the sucrose accumulation,and 0.5 mM/L NAA had opposite effect.0.5 mM/L NAA treatment significantly promote the accumulation of glucose.NAA treatment had significantly inhibitory effect to sorbitol concentration,the effect of 0.5 mM/L NAA treatment is more significant at mature period.6.The expression level of SPS2(Sucrose phosphate synthase)gene was significantly promoted under 0.5 mM/L?1.25 mM/L GA4+7 and 0.25 mM/L NAA treatment in both two varieties.However,it was inhibited under 0.5 mM/L NAA.In 'Huyou 018' fruit,1.25 mM/L GA4+7 treatment inhibited the expression of NAD+-SDH(sorbitol dehydrogenase)gene.0.5 mM/L NAA treatment significantly inhibited the expression of SS1(Sucrose synthase)gene.In 'Jinxiu'yellow peach both 0.5 mM/L and 1.25 mM/L GA4+7 treatments could significantly increasethe expression of SOT2(sorbitol transporter)and SS2 genes in the early development of fruit.7.The expression level of SOT1,SOT2 and NI(neutral invertase)geneswere significantly different between the two cultivars.All these three genes expressed higher in the fruit of 'Huyou 018' than that in'Jinxiu'yellow peach,SPS2 gene showed a high expression level both in the two varieties of peach fruit,which is the major gene that regulate sucrose accumulation during the late stages of peach and nectarine fruit development.However,the expression level of both SS1 and SS2 genes were quite low in both two varieties and reduced during the development stage,they mainly had an effect on the regulation of sucrose accumulation in the early stage of fruit development.